Voltage regulator



Oct. 11; 1966 JyF. WALT-ON 3,278,832

I VOLTAGE REGULATOR Filed May 4. 1962 INVENTOR JOHN F. WALTON ATTORNEYSUnited States Patent 3,278,832 VOLTAGE REGULATOR John F. Walton, McLean,Va., assignor, by mesne assignments, to Halliburton Company, acorporation of Delaware Filed May 4, 1962, Ser. No. 192,483 16 Claims.(Cl. 323-22) The present invention relates to voltage regulator circuitsand more particularly to shunt and series-connected circuits forregulating the voltage output of negative volttage supplies.

Shunt and series regulator circuits for positive voltage supplies arequite common in the prior art and are extensively employed. With regardto negative voltage supplies series regulator circuits are quite common,the series regulating tube normally being connected in the groundedvoltage bus so as to obtain suitable operating potentials. This type ofcircuit may be readily employed where the negative supply is independentof a positive supply but where a circuit is to supply both positive andnegative output voltages relative to ground potential, the connection ofthe series regulator tube of the negative supply in the ground returnlead presents considerable difficulty. More specifically, where a powersupply provides both positive and negative voltages and employs a commonground return lead, location of the series regulator tube or tubes ofthe negative supply in this lead affects the positive voltage supplywhenever there is an adjustment in the negative voltage circuit. Inorder to avoid this interaction of the regulator circuits, additionalcircuitry must be employed to produce an adjustment in the positivesupply whenever an adjustment is made in the negative supply. It has notbeen possible previously to connect the series regulator tube for thenegative supply in the negative voltage lead since, in order to do so,the cathode of the series regulator tube must be connected to thenegative output voltage of the rectifier and filter circuit and theanode must be connected to the negative supply output terminal which isnormally less negative than the aforesaid voltage. Since the cathode isconnected directly to the output from the rectifier circuit, it isconnected to the most negative potential subsisting in the circuit andin consequence it is not possible to obtain a suitable bias voltage forthe grid of this regulator tube.

It is an object of the present invention to provide a series regulatorcircuit for a negative voltage supply in which the series regulator tubemay be connected in the negative voltage bus.

Difiiculty is also experienced in attempting to employ shunt regulatorcircuits in negative voltage supply systems regardless of whether thenegative voltage supply is employed independently or is utilized inconjunction with a positive supply. The reason for this difficulty isthat in the normal shunt control circuit, a resistor is connected inseries with the negative voltage bus and the current through thisresistor is varied by means of shunt connected tubes. The cathodes ofthe shunt tubes are connected to the negative output terminal or leadand there is no readily available voltage for biasing the grids of thetubes negative with respect to the cathodes. It is undesirable toutilize cathode bias resistors since such resistors must have arelatively high impedance and materially reduce the current that can bedrawn through any given shunt regulator tube. In order to provide acircuit having a given percentage of regulation, a larger number ofshunt connected tubes must be employed where cathode bias is utilizedthan if cathode bias is not required.

It is therefore another object of the present invention to provide ashunt regulator circuit for negative supplies in which a suitable biasvoltage for the control grid of the shunt regulator tube or tubes may beobtained without resort to the use of cathode bias resistors connectedin series with the cathode circuit of the tubes.

In accordance with the present invention, there is provided a voltageregulator circuit in which an error signal indicating deviation of anegative output voltage from a desired value is amplified in anamplifier in which a distinct, small and low capacitance power supply isemployed to supply the anode voltage for the output stage of theamplifier. This power supply is connected between the anode and the loadresistor of this last stage of amplification. The load resistor isreturned to the negative output bus and due to the location of the laststage power supply and the load resistor as set forth above, thejunction of the load resistor and the individual power supply isnegative relative to the voltage of the negative output bus. Inconsequence, by appropriately proportioning the values of the voltage ofthe individual supply, the quiescent current through the last stage ofamplification and the value of a load resistor, a suitable bias may beobtained for the control grid of the control tube whether it be a seriesor shunt connected control tube.

By connecting the junction of this individual power supply and the loadresistor directly to the control grids of the regulator tube or tubes,the proper operating potential is developed directly on the controlgrids and also the signal currents which are developed across this loadresistor are directly coupled to the control grids. The circuittherefore is a direct coupled circuit having excellent response to highfrequency transients and exhibiting low drift characteristics. The shuntcapacity to ground .of the individual power supply tends to by-pass thehigh frequency signal components of the control voltage and therefore itis necessary that the individual power supply have a low shunt capacityto ground. This capacity should be of the order of 20 micro-micro-faradsin order to prevent undue loss of signals up to one megacycle persecond. A power supply suitable for such a use is disclosed and claimedin US. Patent No. 2,914,719 of Walton et al. assigned to the assignee ofthe present invention.

It is therefore, another object of the present invention to provide avoltage regulator circuit for negative voltage supplies in which aseparate power supply is employed as an anode supply for the last stageof an error signal amplification circuit and is further employed as ameans for coupling the error signal to a control tube 0 as to develop asuitable operating bias on the control grid of the voltage control tubeor tubes.

It is still another object of the present invention to provide a seriesconnected voltage regulator circuit for negative voltage supplies inwhich the series regulator tube is connected in the negative voltage busor lead and in which a distinct volt-age source is employed for the laststage of an error signal amplification circuit in order to developappropriate operating bias on the control grid of the series regulatortube.

Yet another object of the present invention is to provide ashunt-connected regulator circuit for negative voltage supplies in whicha distinct power supply is employed for the anode circuit of the laststage of the signal amplification circuit in order to develop anappropriate operating bias on the control grids of the shunt connectedtubes without requiring the use of cathode resistors in conjunction withthe regulator tubes.

It is still another object of the present invention to provide a voltageregulator circuit for negative voltage supplies in which a separatepower supply is employed to couple an error signal from an error signalamplification circuit to the control grid of a regulator tube so as toprovide a proper operating bias on the control grid relative to thecathode of the regulator tube.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of several embodiments thereof,especially when taken in conjunction with the accompanying drawings,wherein:

FIGURE 1 is a schematic electrical diagram of the series regulatorcircuit incorporating the principles of the present invention; and

FIGURE 2 is a schematic electrical diagram of a shunt regulator circuitemploying the principles of the present invention.

Referring now specifically to FIGURE 1 of the accompanying drawings,there is illustrated a series regulator circuit for use with a negativevoltage supply. A transformer 1 is provided with a primary circuit 2adapted to be connected to AC. power line and a secondary circuit 3having its upper end, as illustrated in FIGURE 1, connected to agrounded bus 4. The lower end of the secondary circuit 3 is connectedthrough a half-Wave rectifier or diode 6 to a junction 7, connectedthrough a filter capacitor '8 to the grounded bus 4. The circuit thusfar described provides a half-wave rectified negative power supply whichis illustrated for purposes of explanation only, it being understoodthat a full Wave bridge rectifier,

voltage doubler circuit, or other conventional rectifier arrangementsmay be employed. Also, the filter circuit which is represented hereinonly by the capacitor 8 may comprise a more elaborate filter circuit,such circuits being conventional in the art.

The circuit of FIGURE 1 further comprises a series regulator tubegenerally designated by the reference numeral 9 which constitutes a dualtriode including a first section having acathode 11, control grid 12 andanode 13. The dual regulator also includes a second section having acathode 14, control 16 and an anode 17. The cathodes 11 and 14 areconnected through voltage dropping resistors 18 and 19 respectively tothe junction 7 and the anodes 13 and 17 are connected together and to anegative output voltage 'bus 21. The negative voltage to be regulatedappears between the buses 21 and 4 and connection may be made to outputterminals 22 and 23 respectively.

An error signal detection and amplification circuit includes a voltagedivider having a fixed resistor 24, a second fixed resistor 26, and afixed resistor 27 having a variable tap 28 adapted to slide thereover.The resistors 24, 26 and 27 are connected in series between the leads 4and 21 with the resistor 27 connected between the resistors 24 and 26.The slider 28 is connected to a grid 29 of a triode 31 having a cathode32 and an anode 33. The cathode 32 is connected through a voltageregulator tube 34 to the negative voltage bus 21 and is furtherconnected through a voltage regulator tube 36 and a resistor 37,connected in series, to the grounded bus 4 with the resistor 37 havingone end directly connected to the grounded bus. The glow tubes 34, 36and resistor 37 constitute a voltage divider which is adapted toestablish a fixed negative potential on the cathode 32 of the tube 31and which therefore serves as a voltage reference for the regulatorsystem.

The anode 33 of the tube 31 is directly connected to a cathode 38 of afurther triode 39 having a control grid 41 and an anode 42. The controlgrid 41 is connected to the junction of the glow tube 36 and theresistor 37 and therefore has a fixed potential established thereon. Theanode 42 of the tube 39 is connected via a lead 43 to a positive voltageterminal of a low capacity power supply 44 having a negative terminalconnected to a junction point 46. The junction point 46 is connectedthrough a first resistor 47 to the control grid 12 of the first sectionof the tube 9 and is also connected through a second resistor 48 to thecontrol grid 16 of the second section of the tube 9. The junction 46 isalso connected through a load resistor 49 to the junction 7 previouslydescribed.

The tubes 31 and 39' constitute a cascode amplifier circuit, this typeof circuit being employed because of the high gain which may be obtainedWith a relatively small number of tubes. The voltage developed at theanode 42 of the tube 39 must be such relative to the voltage of thecathode 32 to permit the tubes 31 and 39 to operate in their normaltransconductance regions. The voltage on the anode 42 is developed bythe power supply 44 which has its negative terminal connected to thejunction point 46. It will be noted that since current through anelectron tube flows from the anode to the cathode, current flows throughthe load resistor 49 from the left to the right as viewed in FIGURE 1.In consequence, the junction point 46 is negative relative to thejunction point 7 and by suitably choosing the voltage of supply 44 andthe quiescent voltages on the control grid 29 and cathode 32 and thevalue of the resistor 49, a suitable bias voltage may be developed onthe grids 12 and 16 of the tube 9. In a typical example, if the voltageat the junction 7 is at, for instance, minus 500 volts and the lead orbus 21 is to be maintained at minus 400 volts, the voltage of the supply44 should be approximately 55-0 volts in order to raise the anode 42 toa negative voltage of no less than minus 200 vol-ts. In such a system,the cathode 32 should be operated at minus 315 volts and the grid 41 atminus 250 volts. Under no signal conditions, the grid 29 should be at anegative potential relative to the cathode 32 and should establish classA operation for the cascade amplifier circuit. The slider 28 ispositioned on the resistor 27 so as to establish a predetermined voltageon the bus 21 and in the event of deviation of this voltage therefromthe voltage on the grid 29 is varied. For instance, if the voltage onthe bus 21 becomes less negative relative to the grounded bus 4 than isdesired, the cathode 32, being directly connected to the bus 21, is moreaffected by the voltage change than the grid 29 and the bias on the tube31 is increased. Thus, triodes 31 and 39 function as a differentialcascode amplifier to derive an error signal indicative of the differencebetween the reference potential at cathode 32 and the load voltageindicating signal supplied to grid 29.- Conduction through the cascodeamplifier is decreased and current flow through the load resistor 49 isdecreased. This renders the grids 12 and 16 of the tube 9 more positivethan previously and increases conduction through the tube 9. As aresult, the voltage on the lead 21 again becomes more negative andregulation is instituted.

It Will be noted that the error signal amplifier circuit is directcoupled to the regulator tube 9 and therefore the low frequency responseof the system is excellent. The high frequency response of the system isdetermined in part by the interelectrode capacities of the various tubesand further by the shunt capacity to ground of the power supply 44. Moreparticularly, if the power supply 44 has a high leakage capacity toground, this capacity, appearing as a low impedance to high frequences,materially reduces the response of the system to the high frequencycomponents of the error signal. Therefore, the power supply 44 shouldhave a very low shunt capacity to ground and may constitute a powersupply as disclosed and claimed in the aforesaid US. patent. The shuntcapacity to ground of the power supply disclosed in the aforesaid patentis between 15 and 20 micro-microfarads so that the high frequencyresponse of the system is very good up .to frequencies of one megacycleper second. The upper range of the response of the system may beextended but the utilization of compensation circuits described inco-pending application Ser. No. 777,037, filed November 28, 1958, forWide Band Direct Coupled Amplifier by J. H. Reaves and J. F. Walton.

Another important feature of the circuit of FIGURE 1 is that the tubes31 and 39 constitute a constant current circuit which is substantiallyindependent of variations of the voltage at the anode 42 over a largerange of values. In consequence, the AC. operating potential to thegrid-cathode circuits of the tube 9 is substantially independent ofvariations in the unregulated output voltage appearing at terminal 7 andis dependent only on variations in the regulated output voltage whichare applied to the grid 29 of tube 31.

It is apparent from the above description that the power supply 44serves as an element for isolating the regulator control circuit fromthe very low voltages at which the regulator tube 9 must be operated.The difference in operating levels between these two circuits may bequite large and is limited only by the convenience of obtaining specificphysical and electrical characteristics in a power supply connected asthe source 44 in FIGURE 1 of the accompanying drawings. In practice lowcapacity supplies of 2500 to 3000 volts have been found to be entirelypractical and such supplies may be employed in circuits of the typeillustrated in FIGURE 1 where the disparity in voltages between thecontrolling and controlled circuits are considerably greater than thoseset forth above for purposes of explanation.

The important feature of the circuit of FIGURE 1 is that the seriesregulator tube may be connected in the negative side of the negativevoltage supply and regulation obtained completely independently of anycircuits employed to regulate a positive voltage which may be developedby circuits employing a common return or ground bus such as the bus 4illustrated in FIGURE 1. As indicated above, this capability resultsfrom the utilization of the low capacity power supply 44 which, as aresult of its connection between the load resistor 49 and the anode 42of the tube 39 develops a voltage at the junction of the load resistorand the supply which is more negative than the voltage of the cathodes11 and 14 of the tube 9; that is, develops a voltage at the junction 46which is lower than the lowest voltage supplied by the power supplywhose voltage is to be regulated.

The principles of utilization of the isolated power supply to developthe necessary negative voltage on the grid of the control tube relativeto its cathode, where the cathode is operating at near the most negativepoint in the circuit, may also be applied to a shunt regulator circuitas illustrated in FIGURE 2 of the accompanying drawings. The unregulatednegative voltage; that is, the voltage from a rectifier power supply orother source of negative potential, is connected between a bus 51 and agrounded bus 52. A resistor 53 is connected between the bus 51 and anegative voltage supply bus 54 connected to an output terminal 56, therealso being an output terminal 57 connected to the grounded voltage bus52. In order to obtain regulation of the voltage on the negative voltagebus 54 varying amounts of current are drawn through the resistor 53 andunder control of a regulator connected in shunt with the terminals 56and 57. More particularly, there are provided four tubes, all of whichare generally designated by the reference numeral 58, connected inparallel and having their anodes 59 connected to the grounded voltagebus 52 and their cathodes 61 connected through current limitingresistors 62 to the negative voltage bus 54. Control grids 63 of tubes58 are all connected to a common lead 64 connected in turn to a junctionpoint 66 adapted to have an error signal potential applied thereto.

By appropriately regulating the error voltage applied to the junctionpoint 66, the current flow through the tubes 58 may be controlled sothat the current flowing through the resistor 53 is at all times such asto maintain a predetermined potential on the bus 54.

The resistors 62 in the cathode circuits of the tubes 58 are quite smalland may be entirely eliminated. They are employed strictly to preventexcessive currents from being drawn through the tubes 58 in the event ofmalfunction which currents would tend to destroy the tubes if theresistors 62 were not employed. If this safety feature -is not desiredthen the resistors 62 may be completely eliminated. The reason formaintaining the resistor 62 at a very low value is to permit the circuitto control a large range of selected negative potentials on the bus 54with a relatively small number of tubes. By employing small valueresistors in the cathode circuit of the tubes, the maximum currentthrough the tubes 58 is limited almost entirely by theircharacteristics. By appropriate selection of the tubes, the range ofquiescent currents that may be established with a given number of tubesis large and consequently the range of voltages over which the outputvoltage may be varied is large relative to the number of tubes connectedin parallel. The advantage to employing large resistors in the cathodecircuit is that a proper operating grid-cathode bias may be obtainedthereby. However, in accordance with the present invention, it is notnecessary to employ the large resistors to obtain the requisite bias andtherefore the cathode resistors may be either eliminated or held to avery small value to provide the advantages indicated above.

Proceeding with the description of the circuit for developing thecontrol voltage to be applied to the junction point 66, there isprovided a voltage divider between the buses 54 and 52 comprising aresistor 67 having one end connected to the bus 52, a resistor 68 havingone end connected to the bus 54 and a resistor 69 connected between theresistor 67 and 68. A tap 71 is adapted to slide along resistor 69 toprovide for adjustment of the voltage to be maintained on the lead 54.The tap 71 is connected to a grid 72 of a first section of a twin triode73 connected as a differential amplifier. The first or left section ofthe tube 73 further comprises a cathode 74 connected to a cathode 76 ofa second section of the tube 73, the two cathodes being connectedthrough a large resist-or 77 to the negative voltage bus 54. An anode 78of a first section of the tube 73 is directly connected to a cathode 79of a first section of a second twin triode 81 having an anode 82connected to the bus 52. An anode 83 of the second section of the tube73 is connected directly to a cathode 84 of a second section of the tube81 having an anode 86 connected to a positive terminal of a low capacitypower supply 87. The negative terminal of the supply 87 is connected tothe junction point 66 which in turn is connected through a load resistor88 to the negative voltage bus 54. In order to provide fixed operatingpotentials for a control grid 89 of the second section of the tube 73,and control grids 91 and 92 of the triode 81 there is provided aresistor and voltage regulator tube network. This network includes aresistor 93 having its upper end connected to the grounded bus 52 andits lower end connected through a first regulator tube 94 to thenegative voltage bus 54. There is further provided three resistors 96,97 and 98 connected in series in the order mentioned between thenegative voltage bus 52 and a junction point 99. The junction point 99is connected through a by-pass capacitor 101 to the negative voltage 54and is also connected to the junction of the resistor 93 and a regulatortube 94. The junction 99 is connected through a resistor 102 to thecontrol grid 89 of the tube 73 and is also connected through a secondvoltage regulator tube 103 to the junction of the resistors 96 and 97.

The voltage regulator tube 94 maintains the voltage at the junctionpoint 99 at a fixed potential depending upon the voltage to bemaintained on the negative voltage bus 54 and therefore maintains thecontrol grid 89 of the second section of the twin triode 73 at a fixedpotential. Similarly, the second voltage regulator tube maintains thevoltage drop across resistors 97 and 98 at a fixed potential dependingupon the voltage on the negative voltage bus 54 and in consequence,maintains the control 7 grids 91 and 92 of the tube 81 at a fixedpotential, depending upon the desired negative output voltage.

The resistors 67, 68 and 69 on the one hand and the tubes 81 and 73 andresistor 77 on the other constitute two parallel voltage dividers. Therelative values of the various impedances in the two voltage dividersmust be such that upon a change in voltage on the negative voltage bus54, the initial change in voltage on the cathodes 74 and 76 is greaterthan the initial change voltage on the grid 72. This may be accomplishedby making the value of the resistor 77 small relative to the value ofthe resistor 68.

In operation, if it is assumed that the voltage on the bus 54 becomesmore negative than the desired value, the change in voltage has moreeffect upon the cathode 74 than upon the grid 72 and, in eflect, thegrid 72 swings positive relative to the cathode. This increases currentflow through the first or left hand section of the tube 73 and due tothe differential eifect in the amplifier decreases current flow throughthe right hand or second section of the tube 73. The voltage at thepoint 67 becomes more positive relative to the bus 54, and current flowthrough the tubes 58 is increased. The increase in current flow causesan increased voltage drop through the resistor 53, thereby causing thevoltage bus 54 to become less negative and completes the regulatingaction.

The utilization of the low capacitance power supply 87, which may be ofthe same type as described relative to the power supply 44 of FIGURE 1,is employed to obtain a proper operating bias on the grids 63 of thetubes 58. As previously indicated, the resistors 62 may be eithereliminated or if employed are of such a low impedance as not to provideaproper operating bias for the tubes. Since the voltage 54 is the mostnegative voltage in this portion of the system, some means must beprovided for obtaining a voltage on the grid 63 negative relative to thevoltage on the negative voltage bus 54. This is accomplished by theutilization of the particular connection of a low capacity power supplybetween the anode 86 'of the tube 81 and the load resistor 88 of thedifierential amplifier. As a result of the fact that current flowthrough the resistor 88 is in an upward direction, as viewed in FIGURE2, the junction 66 is maintained at a potential negative relative to thebus 54 whenever current is drawn through the resistor. The extent towhich the junction 66 is negative relative to the cathode is determined,under no signal conditions, by the quiescent or no signal currentflowing through the right hand stage of the differential amplifier andby the value of the resistor 88. These two parameters are chosen suchthat a proper potential is obtained at the junction point 66. Thesefactors also determine the value of the voltage provided 'by the powersupply 8 7 and if in the typical example the tubes 58 are tube types6BL7, the tubes 81 and 73 are tube types 6922 and the load resistor 88is 220,000 ohms then in order to produce a voltage range on the bus 54of from minus 350 to minus 450 volts, the power supply 87 should providea voltage of at least 250 volts D.C.

As previously indicated with respect to FIGURE 1, the degree ofregulation obtainable is a function of the amplification factor providedby the control system. In consequence a diiferential cascode amplifierwhich includes the tubes 73 and 81 is employed to provide maximum gainwith a minimum number of tubes, it being found that for most purposes,the gain produced by these tubes is sufiicient to obtain good regulationof the circuit; that is regulation within plus or minus one-half of onepercent of the selected voltage. Increased regulation may be obtained bysimply cascading stages of amplification and/ or employing more tubes inparallel with the tubes 58.

While I have described and illustrated several embodiments of myinvention, it will be clear that variations of the details ofconstruction which are specifically illustrated and described may beresorted to Without departing from the true spirit and scope of theinvention as defined in the appended claims.

What I claim is:

1. A voltage regulator circuit for a D.C. load responsive to a D.C.source comprising an electron tube responsive to said source, said tubehaving at least a cathode, an anode and a control grid, means connectingsaid electron tube to vary the potential across said load in response tovariations in current through said tube, a control circuit connected tosaid load for developing a signal voltage indicative of the voltageacross said load, said control circuit having an output stage includinga second electron tube connected to said control circuit, said secondelectron tube comprising a sec-ond cathode and a second anode, an anodevoltage supply, a load resistor connected to the grid of said firstelectron tube, means connecting said anode supply between one terminalof said load resistor and the grid of said first electron tube and saidanode of said second electron tube, the other terminal of said loadresistor being connected to a supply terminal, and means connecting saidcontrol grid to said load resistor.

2. A series voltage regulator circuit for a D.C. load responsive to anunregulated D.C. supply comprising a pair of leads connected across saidload and having a voltage to be regulated developed thereacross, oneterminal of said supply and one of said leads having a commonconnection, an electron tube having a cathode, an anode and a controlgrid, said cathode being connected to the other terminal of said supply,said other terminal and the other of said leads being at negativepotential relative to said common connection, said anode being connectedto said other lead, a control circuit for developing an error voltageproportional to variations in the voltage across said load from apredetermined value, a source of potential, and means for connectingsaid error voltage to said control grid through said source ofpotential, said source of potential being such as to establish a properoperating bias on said control grid relative to said cathode of saidelectron tube.

3. The combination according to claim 2 wherein said control circuitcomprises plural stages and has a final stage including a secondelectron tube, said second electron tube having a second cathode and asecond anode, means connecting said second cathode to said other lead, aload resistor and means connecting said anode of said second tubethrough said source of potential to said load resistor and meansconnecting said load resistor between said control grid and said cathodeof said first-mentioned electron tube.

4. The combination according to claim 3 wherein said control circuitincludes a diflerential amplifier and wherein said final stage of saidcontrol circuit constitutes one section of said differential amplifier.

5. The combination according to claim 4 wherein said diiferentialamplifier is a cascode amplifier.

6. A shunt voltage regulator for a D.C. load responsive to a D.C. sourcecomprising a pair of leads having an unregulated voltage developedthereacross, an output terminal connected to said load, a resistorconnected between one of said leads having the more negative voltagedeveloped thereon and said output terminal, an electron tube having ananode, a cathode and a control grid, said cathode being connected tosaid output terminal and said anode being connected to the lead of saidpair of leads having the more positive voltage developed thereon, acontrol circuit including a cascode difierential amplifier fordeveloping an error voltage proportional to the deviation of the voltageon said output terminal from a predeterminable value, said controlcircuit being responsive to a signal proportional to the D.C. voltageacross said load, and including a second electron tube, said secondelectron tube comprising a second cathode and a second anode, a sourceof potential connected to said second anode, and means for applying saiderror voltage to said control gnid through said source of potential,said source having a voltage and being poled such that said control gridhas an operating bias developed thereon relative to said cathode.

7. A shunt voltage regulator for a D.C. load responsive to a D.C. sourcecomprising a pair of leads having an unregulated voltage developedthereacross, an output terminal, a resistor connected between the leadhaving the more negative voltage developed thereon and said outputterminal, an electron tube having an anode, a cathode and a controlgrid, said cathode being connected to said output terminal and saidanode being connected to the lead of said pair of leads having the morepositive voltage developed thereon, a control circuit connected to saidload for developing a signal voltage proportional to the deviation ofthe voltage on said output terminal from a predeterminable value, saidcontrol circuit being responsive to a signalv proportional to the D.C.voltage across said load, said control circuit having an output stageincluding a second electron tube, said second tube having an anode, aload impedance, a source of potential connected between and couplingsaid signal voltage between said anode of said second tube and said loadimpedance, and means connecting said control grid to said loadimpedance, said source having a voltage and being poled such as toprovide an operating control grid bias for said first-mentioned tube andto provide the anode potential for said second tube.

8. The combination according to claim 7 wherein said control circuitincludes a differential amplifier and wherein said output stagecomprises one section of said differential amplifier.

9. The combination according to claim 8 wherein said differentialamplifier in a cascode amplifier.

10. A circuit for regulating the D.C. potential across a load despitevariations in a first D.C. source coupled to the load and in the loadimpedance comprising means for establishing a D.C. voltage referencelevel, means responsive to the voltage across said load and said voltagereference level for deriving an error signal indicative of thediiference between said load and reference voltages, said last-namedmeans including a first discharge device having a first emitter ofcharged carriers, a first collector for said carriers and a firstcontrol electrode for controlling the fiow of charged particles betweensaid first emitter and first collector, said first control electrodebeing responsive to a signal proportional to the D.C. voltage acrosssaid load, a variable regulating impedance in series between said loadand said first source, said impedance including a second electrondischarge device having a second emitter of charged particles, a secondcollector for said particles and a second control electrode forcontrolling the flow of charged particles between said second emitterand collector, a second D.C. voltage source connected between said firstcollector and second control electrode, the impedance of said secondvoltage source being such that said error signal is coupled between saidfirst collector and second control electrode, said second voltage sourcebeing connected in series with said first emitter and first collectorfor energizing the emitter collector path of said first dischargedevice, means for connectingthe emitter collector path of said seconddischarge device to be energized by said first D.C. source, theamplitude of said second voltage source being sufficient to bias saidfirst collector electrode so that it collects said charged particles andto bias said second control electrode so that it is biased at a morenegative voltage than the high voltage terminal of said first D.C.

source.

11. The circuit of claim 10 wherein said second discharge device is inseries between said first D.C. source and said load.

12. The circuit of claim 10 wherein said second dis charge device is inshunt between said first D.C. source and said load.

13. The circuit of claim 10 further including a load impedance for saiderror voltage, said load impedance being connected in a D.C. circuitbetween said second emitter and second control electrode.

14. A circuit for regulating the D.C. potential across a load despitevariations in a first D.C. source coupled to the load and in the loadimpedance comprising means for deriving an error signal indicative ofthe voltage across said load, said last-named means including a firstdischarge device having a first emitter of charged carriers, a firstcollector for said carriers and a first control electrode forcontrolling the flow of charged particles between said first emitter andfirst collector, a D.C. path between one side of said load and saidfirst emitter, said first control electrode being responsive to a signalproportional to the D.C. voltage across said load, a variable regulatingimpedance in series circuit between said load and said second source,said impedance including a second electron discharge device having asecond emitter of charged particles, a second collector for saidparticles and a second control electrode for controlling the flow ofcharged particles between said second emitter and collector, a secondD.C. voltage source connected between said first collector and secondcontrol electrode, the impedance of said second voltage source beingsuch that said error signal is coupled between said first collector andsecond control electrode, said second voltage source being connected inseries circuit with said first emitter and first collector forenergizing the emitter collector path of said first discharge device,means for connecting the emitter collector path of said second dischargedevice to be energized by the first D.C. source, the amplitude of saidsecond voltage source being sufficient to bias said first collectorelectrode so that it collects said charged particles and to bias saidsecond contr-ol electrode so that it is biased at a more negativevoltage than the high voltage terminal of the first D.C. source.

15. The circuit of claim 14 further including a load impedance for saiderror voltage, said load impedance being connected in a D.C. circuit,between said second emitter and second control electrode.

16. A circuit for regulating the D.C. potential across a load despitevariations in a first D.C. source coupled to the load and in the loadimpedance comprising means for deriving an error signal indicative ofthe voltage across said load, said last-named means including a firstdischarge device having a first emitter of charged carriers, a firstcollector for said carriers and a first control electrode forcontrolling the flow of charged particles between said first emitter andfirst collector, a D.C. path between one side of said load and saidfirst emitter, said first control electrode being responsive to a signalproportional to the D.C. voltage across said load, a pair of leadsconnected to said first D.C. source and coupled to the load, a resistorconnected between the one of said leads having the more negative voltagedeveloped thereon and the output terminal a variable regulatingimpedance in series between said load and said first source, saidimpedance including a second electron discharge device having a secondemitter of charged particles, a second collector for said particles anda second control electrode for controlling the fiow of charged particlesbetween said second emitter and collector, a second D.C. voltage sourceconnected between said first collector and second control electrode, theimpedance of said second D.C. voltage source being such that said errorsignal is coupled between said first collector and second controlelectrode, said second D.C. voltage source being connected in seriescircuit with said first emitter and first collector for energizing theemitter collector path of said first discharge device, means forconnecting the emitter collector path 11 v12 of said second dischargedevice to be energized by said 2,398,916 4/1946 Brewer 32322 first D.C.source. 2,569,945 10/1951 Netteland 32322 2,760,144 8/1956 Crandon323-22 References Cited by the Examiner 1 4g7 10 3 9 4 Knoop 323 31' XLLOYD MCCOLLUM, Examlner- 2,075,966 4/ 1937 Vance 32322 K. W. HADLAND,K. D. MOORE, Assistant Examiners.

10. A CIRCUIT FOR REGULATING THE D.C. POTENTIAL ACROSS A LOAD DESPITEVARIATIONS IN A FIRST D.C. SOURCE COUPLED TO THE LOAD AND IN THE LOADIMPEDANCE COMPRISING MEANS FOR ESTABLISHING A D.C. VOLTAGE REFENCELEVEL, MEANS RESPONSIVE TO THE VOLTAGE ACROSS SAID LOAD AND SAID VOLTAGEREFERENCE LEVEL FOR DERIVING AN ERROR SIGNAL INDICATIVE OF THE DIFFERNCEBETWEEN SAID LOAD AND REFERENCE VOLTAGE, SAID LAST-NAMED MEANS INCLUDINGA FIRST DISCHARGE DEVICE HAVING A FIRST EMITTER OF CHARGED CARRIERS, AFIRST CONTOR FOR SAID CARRIERS AND A FIRST CONTROL ELECTRODE FORCONTROLLING THE FLOW OF CHARGED PARTICLES BETWEEN SAID FIRST EMITTER ANDFIRST COLLECTOR, SAID FIRST CONTROL ELECTRODE BEING RESPONSIVE TO ASIGNAL PROPORTIONAL TO THE D.C. VOLTAGE ACROSS SAID LOAD, A VARIABLEREGULATING IMPEDANCE IN SERIES BETWEEN SAID LOAD AND SAID FIRST SOURCE,SAID IMPEDANCE INDCLUDING A SECOND ELECTRON DISCHARGE DEVICE HAVING ASECOND EMITTER OF CHARGE PARTICLES A SECOND COLLECTOR FOR SAID PARTICLESAND A SECOND CONTROL ELECTRODE FOR CONTROLLING THE FLOW OF CHARGEDPARTICLES BETWEEN SAID SECOND EMITTER AND COLLECTOR, A SECOND D.C.VOLTAGE SOURCE CONNECTED BETWEEN SAID FIRST COLLECTOR AND SECOND CONTROLELECTRODE, THE IMPEDANCE OF SAID SECOND VOLTAGE SOURCE BEING SUCH THATSAID ERROR SIGNAL IS COUPLED BETWEEN SAID FIRST COLLECTOR AND SECONDCONTROL ELECTRODE, SAID SECOND VOLTAGE SOURCE BEING CONNECTED IN SERIESWITH SAID FIRST EMITTER AND FIRST COLLECTOR FOR ENERGIZING THE EMITTERCOLLECTOR PATH OF SAID FIRST DISCHARGE DEVICE, MEANS FOR CONNECTING THEEMITTER COLLECTOR PATH OF SAID SECOND DISCHARGE DEVICE TO BE ENERGIZEDBY SAID FIRST D.C. SOURCE. THE AMPLITUDE OF SAID SECOND VOLTAGE SOURCEBEING SUFFICIENT TO BIAS SAID FIRST COLLECTOR ELECTRODE SO THAT ITCOLLECTS SAID CHARGED PARTICLES AND TO BIAS SAID SECOND CONTROLELECTRODE SO THAT IT IS BIASED AT A MORE NEGATIVE VOLTAGE THAN THE HIGHVOLTAGE TERMINAL OF SAID FIRST D.C. SOURCE.